1. Field of the Invention
The present invention relates to a wiring board and its manufacturing method, more specifically, to a wiring board having a high-density wiring section and a method for manufacturing such a wiring board.
2. Description of Background Art
As a multilayer printed wiring board for mounting an IC chip (semiconductor element), a type of wiring board has interlayer resin insulation layers and conductive layers are alternately laminated on a resin core substrate having through-hole conductors, and the conductive layers are connected by via-hole conductors.
IC chips have become finer and more highly integrated recently, and the number of pads formed on the uppermost layer of a packaging substrate is increasing, leading to further fine-pitched pads. Following such pads with finer pitches, the wiring pitches of a packaging substrate are also rapidly becoming narrower (see International Publication No. 2007/129545, for example).
High-density wiring is formed in part of such a wiring board. An electronic component is incorporated in interlayer resin insulation layers of the wiring board; and the electronic component is formed by arranging a high-density wiring layer on a substrate made of heat-resistant material such as silicon and glass with a low thermal expansion coefficient. The entire contents of this publication (these publications) are incorporated herein by reference.